There a re (are) a few items missing

Five tiny mistakes - there/their/they're, your/you're, its/it's, apostrophe misuse, and affect/effect - cause most small-but-visible errors. Below are quick checks, many wrong→right pairs for work, school, and casual contexts, copyable rewrites, and memory tricks to spot fixes instantly.

If you want a fast answer, start at Quick answer and grab a rewrite from Examples or Rewrite help.

Quick answer: one-line tests

Substitution checks: replace with "they are", "you are", or "it is" - if the sentence still makes sense, use they're/you're/it's. Use their/your/its for possession (no apostrophe). Apostrophes never make regular plurals. For affect/effect: action = affect (verb); result = effect (noun).

there = place or existence; their = possessive; they're = they are.
your = possessive; you're = you are.
its = possessive; it's = it is / it has.
Apostrophes mark possession or contractions only-don't use them for standard plurals (1990s, As, CDs).
affect (verb) = to influence; effect (noun) = the result.

Core explanation: the short rules you need

Use substitution and a simple logic test instead of memorizing quirks: expand contractions, ask who owns what, and decide whether you mean action or result.

Contraction test: expand to "they are", "you are", or "it is/it has". If that fits, use the contraction.
Possession test: if someone or something owns the item, use the possessive with no apostrophe for its/your/their.
Apostrophe rule: use for contractions (don't) or possession (Sara's phone), not for plurals.
Affect/effect: replace with "influence" or "result" to pick the correct word.

there - "There is a problem." (place/existence)
their - "Their folder is on my desk." (possession)
they're - "They're available after lunch." (contraction)
your - "Is that your badge?" (possession)
you're - "You're on the list." (contraction)
its - "The company altered its policy." (possession)
it's - "It's been updated." (contraction)
affect - "The delay will affect delivery." (verb)
effect - "The effect was immediate." (noun)

Real usage: tone and where to be strict

Match formality to audience. Be stricter in reports and academic work; be natural in casual messages. Regardless of tone, errors that change meaning always need fixing.

Formal: avoid contractions and double-check possession and affect/effect.
Business: contractions are fine, but verify your/you're and its/it's before sending.
Casual: contractions are expected; possessives and apostrophes still matter.

Work:
Wrong: "Their submitting the quarterly numbers tomorrow." →
Right: "They're submitting the quarterly numbers tomorrow."
School:
Wrong: "Its obvious the data is noisy." →
Right: "It's obvious the data are noisy." (also check agreement)
Casual:
Wrong: "Your coming to the party, right?" →
Right: "You're coming to the party, right?"

Examples: wrong → right pairs you can copy

Grouped by context so you can choose a ready-to-paste correction.

Work - Wrong: There agenda was missing from the packet. →
Right: Their agenda was missing from the packet.
Work - Wrong: Their planning to extend the deadline. →
Right: They're planning to extend the deadline.
Work - Wrong: The policy change will effect employee morale. →
Right: The policy change will affect employee morale.
Work - Wrong: The effect of the change was immediate. →
Right: The effect of the change was immediate.
School - Wrong: The experiment lost it's control sample. →
Right: The experiment lost its control sample.
School - Wrong: Its surprising how much the temperature affected the results. →
Right: It's surprising how much the temperature affected the results.
School - Wrong: I got straight A's this semester. →
Right: I got straight As this semester.
Casual - Wrong: Your gonna love this new cafe. →
Right: You're gonna love this new cafe. (Prefer: "You're going to love this new cafe.")
Casual - Wrong: There new playlist is fire. →
Right: Their new playlist is fire.
Casual - Wrong: I bought some apple's at the store. →
Right: I bought some apples at the store.
Work - Wrong: Your report needs more data analysis. →
Right: Your report needs more data analysis.
School - Wrong: The redesign effected customer usage. →
Right: The redesign affected customer usage.
Work - Wrong: There is many missing fields. →
Right: There are many missing fields.

Rewrite help: copyable templates and fixes

Templates preserve tone while fixing the error. Formal rewrites expand contractions; casual rewrites keep them but correct possessives and apostrophes.

Formal template: expand contractions and state ownership clearly - "They are going to send the invoice today."
Casual template: keep contractions but correct apostrophes - "They're going to send the invoice today."
Affect/effect template: decide whether you mean "influence" (affect) or "result" (effect) and swap accordingly.

Rewrite:
Original: "Their going to send the invoice today." →
Formal: "They are going to send the invoice today." →
Casual: "They're going to send the invoice today."
Rewrite:
Original: "I cant find it's file." →
Correct: "I can't find its file."
Rewrite:
Original: "Your the only one who can approve this." →
Formal: "You are the only person who can approve this." →
Casual: "You're the only one who can approve this."
Rewrite:
Original: "I got 3 B's and a C." →
Correct: "I got 3 Bs and a C."

Try your own sentence

Test the full sentence, not just the word. Context usually makes the right choice obvious. If you want a machine check, paste a single sentence into the widget below.

Memory tricks: one-liners that stick

Use quick rules when proofreading to catch errors fast.

they're → try "they are". If it fits, use they're.
you're → try "you are". If it fits, use you're.
it's → try "it is" or "it has". If neither fits, use its (possession).
Apostrophe rule: contraction or possession = apostrophe; plural = no apostrophe.
Affect = Action (verb). Effect = End result (noun).

Mnemonic: Cover the word-if the sentence still needs a place, it's there; if it needs ownership, it's their; if "they are" works, it's they're.

Similar mistakes to watch for (fast fixes)

Mixing up short words often leads to other small errors. Apply the same substitution or read-aloud check.

then vs than: "then" = time/sequence; "than" = comparison.
lose vs loose: "lose" = misplace; "loose" = not tight.
who vs whom: "who" = subject; "whom" = object (use "who" safely in casual writing).
lay vs lie: "lay" needs an object (lay the book); "lie" does not (I lie down).

Wrong: I will do that then you. →
Right: I will do that than you.
Wrong: The rope is lose. →
Right: The rope is loose.

Punctuation, spacing, hyphenation and small grammar clean-up

These small edits often accompany the five main issues and are quick fixes.

Decades: write 1990s (no apostrophe).
Plurals of letters/grades: As, Bs; use A's only when clarity requires it.
Possessive of names ending in -s: pick one style and use it consistently (James's book or James' book).
Hyphens: use in compound adjectives before a noun (well-known author) but not after the noun.
Spacing: no space before commas/periods; one space after a period is standard in digital text.
Quick grammar check: if expanding a contraction breaks the sentence, you likely chose the wrong word.

Wrong: The 2000's technology was clunky. →
Right: The 2000s technology was clunky.
Wrong: She is a well known author. →
Right: She is a well-known author.

Soft CTA: quick next step

Run the substitution tests (they are / you are / it is; action vs result), read the sentence aloud, then paste a single sentence into a grammar checker or ask a colleague if you're still unsure.

First try the substitution checks in Quick answer.
If still unsure, paste one sentence into a checker for a targeted suggestion and a copyable rewrite.

FAQ

How do I quickly tell their / there / they're apart?

Substitute "they are" - if that fits, use they're. If the sentence shows ownership, use their. Otherwise use there for place or existential phrases ("There is/are").

Is it its or it's after a noun?

Use it's only for "it is" or "it has". Use its for possession. Try expanding to "it is" - if that makes sense, use it's.

Should I use affect or effect in my report?

If you mean "to influence", use affect (verb). If you mean "the result", use effect (noun). Replace with "result" to test for effect.

Can I use contractions like you're in a formal email?

Avoid contractions in formal reports and academic work. In business emails, contractions are acceptable if clarity is preserved.

What's a fast way to check a sentence before sending?

Run the substitution tests, read the sentence aloud, and scan for apostrophes used as plurals. For a second opinion, paste one sentence into a grammar tool that explains the fix and offers rewrites.

Want an instant rewrite?

If one sentence still bothers you, paste it into a grammar checker for highlighted errors and suggested rewrites. Most fixes appear in under 10 seconds after the substitution tests.