how can i download free apps without having to update or add a credit card?

On a mobile device go to Settings > iTunes & App Store > Apple ID and check your payment information is current. Even if you only want something that is free, Apple may insist any current payment method can be verified with your financial institution. You can try removing payment information (see the last two links) to avoid the problem with the existing method but other topics indicate if you have any payment form currently on record it must first be verified before you can change payment type.

- Are you (still) using a valid payment method? --> Payment methods that you can use in the iTunes Store, App Store, and iBooks Store - https://support.apple.com/HT202631 (Discussions on this forum mention some countries do not accept debit cards, and even if they do some items cannot be purchased with debit cards.)

- If your payment method is declined, or you have a billing issue with a previous purchase in the iTunes Store - https://support.apple.com/HT203005 - various reasons why payment method is declined including pending purchases.

- If this abruptly started happening try removing and re-entering your payment information - Change or remove your Apple ID payment information - https://support.apple.com/HT201266

- Do the name, address (all spelling, letter case and punctuation), and card numbers exactly match those you have entered? You didn't mis-type anything?

- You entered the 3 digit security code for the card? Correctly?

- The country for the bank and your address are the same as the iTunes Store country you are using?

- See the end of the document linked above for special measures that may be necessary for some cards, plus about contacting your financial institution to make sure your records match.

If you still have a problem contact Apple:

iTunes Store - Contact Us - https://www.apple.com/emea/support/itunes/contact.html

To remove payment:

Removing a credit card from an account - Change or remove your Apple ID payment information - https://support.apple.com/HT201266 - More information at: https://discussions.apple.com/thread/3251676?answerId=15891166022#15891166022

If you can‘t choose None when you edit your Apple ID payment information - https://support.apple.com/HT203905 - also make sure you don't have any active subscriptions, are set as the Family Organizer for a Family Sharing plan, or owe any money for past purchases.

You don't have to have a payment method on file, but if you have one it must be valid and have available funds.

There are normally some hoops you can jump through as you create your iTunes account that workaround the need for a payment card or bank account, otherwise once the account is set up the iTunes Store may still expect you to provide one, even if you are obtaining free content, which you can later remove. If you don't have or want to use a credit/debit card at this time you can try this method using iTunes on a computer...

1. Enable the menu bar if needed with Ctrl+B (only applies to some builds of iTunes 12 for Windows)
2. Sign out of the iTunes Store from the Store/Account item on the menu bar
3. Go to Music > iTunes Store home page
4. Go to Quick Links > Redeem
5. Sign in with your Apple ID
6. Go through the screens, accepting the EULA, etc. You should arrive at a Review Payment screen where one of the options is None - select this and continue. You shouldn't actually need to redeem a new voucher/card.

It is worth noting that one of the functions of the registration is to prove you have a valid billing address in the region whose store you are trying to use. You might also have difficulty selecting None as an option if you have any active subscriptions (see View, change, or cancel your subscriptions - Apple Support), an outstanding debit balance to the iTunes Store, there are unreleased authorization holds on the card (see About payment card authorization holds in the iTunes Store - Apple Support) or you are trying to switch to one regional store while being in a different region. See If you can't choose None when you edit your Apple ID payment information - Apple Support for more.

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