If you drive through Blackwall or Silvertown tunnel during charging times, you need to pay every time you cross.  Charges apply from 06.00 – 22.00, 7 days a week in both directions and you have until midnight on the third day after your journey to pay.  Non payment will result in a Penalty Charge Notice (PCN).  You can Pay online, download the official TfL Pay to drive in London app which is available to download for free at both the Apple App Store and Google Play Store, or pay by phone: UK: 0343 222 2222 (call charges may apply), International: +44 343 222 2222
Textphone: 020 7649 9123 (if you have impaired hearing).