The $20 invite, and the $2 number that makes it count
@James_Tyneham — you already found the method. What you are missing is the number, and the arithmetic says it is worth buying one properly: an accepted invite returns $20, and a number that passes verification costs $2–12. One accepted invite pays for the line many times over.
one accepted invite = $20
one number that works = $2 – $12
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net, first friend = +$8 to +$18
every friend after = +$20
The five boxes a number ticks before an invite counts
- Carrier-backed, not VoIP — free apps and shared OTP inboxes stop at this box
- Private — a number sold with “public inbox” attached has already been used on ChatGPT
- Fresh on ChatGPT — never verified there before
- A supported country — US, UK and Canada are the safe three
- Held for the month — a line you keep, not a 20-minute burner
Those five boxes are the whole difference between “verification failed” and “credits added”. A guide that walks each box properly.
Real numbers, current prices, no ID needed
- BuyUKeSIM — real UK +44, receives SMS, from $1.99, crypto accepted
- Silent.link — US +1 at $59/year, UK +44 at £59/year, balance never expires
- nadanada — UK +44 rented at $12 per 3 months, extendable
- JMP.chat — real US or Canadian number for calls and texts, $4.99/month, any device
- Crypton.sh — pay per use, no account
Start with the cheapest one. The first accepted invite returns more than the line costs. 
The multiplier that turns one invite into a group
The invite counts per person, not per device, and every person who joins gets $20 as well — so this is a gift you are handing out, not a favour you are asking for. Family, roommates, the class group, the football group.
A message that gets a yes:
Signed up for ChatGPT and they're running a referral — we both get $20 in credits.
You install the desktop app, log in, send one message. That's it.
Want me to send the link?
One account per person keeps the credits sitting in your balance, and it is why the group message beats a list of stranger emails. 
While those invites land, the coding tiers that are already free and need no phone at all 
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GitHub Copilot Free — 2,000 completions + 50 chat messages a month, Claude Sonnet in the model list, the only vendor that prints a hard number
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Cursor free — 2,000 completions and 50 premium requests a month
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Trae — 5,000 auto-completions a month · Qoder — unlimited completions · Windsurf — refreshed daily and weekly quotas
Three pages that keep this list honest, so you never trust a stale number again:
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Which tiers are generous this week — a live directory where every claim carries the date it was last checked
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What each vendor actually limits you to — the hard numbers in one place, updated as they change
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How these tiers behave after a month of real use — the same subject measured, not announced
The lane where nothing is counted at all
Your ChatGPT Plus already includes Codex CLI usage, so check the plan page before farming what you may already pay for. 
Start with the cheapest number. The first accepted invite returns more than the line costs.
The problem:
The fix:
Watch out:
!