it says 'Replace Ink' for a color but the INKvestment tank still looks half full.

Diagnosis

The Brother MFC-J4535DW uses a "calculated consumption" system rather than a precise physical float or optical sensor to measure ink levels. The printer tracks the number of nozzles fired and the amount of ink expelled during print jobs and automatic cleaning cycles. Because the INKvestment tanks have a significantly higher capacity than standard cartridges, the software often miscalculates the remaining volume, especially if you have performed multiple deep cleaning cycles or print high-saturation graphics. When the internal counter reaches a specific threshold, the printer triggers the 'Replace Ink' message regardless of the actual fluid level visible through the tank window. This is a preventative measure to avoid "air sucking," which can cause permanent damage to the print head. You can confirm this is a software estimation error if the print quality remains crisp and saturated despite the warning, or if the ink level visually contradicts the on-screen percentage.

How to Fix It

To bypass the software lock and continue using the remaining ink in your INKvestment tanks, follow these precise steps to reset the ink alert:

1. Press the Stop/Exit button on the control panel to clear the initial warning message.
2. If the message persists, press the Home button to return to the main screen.
3. Navigate to the Ink menu by selecting the ink droplet icon on the touchscreen.
4. Select the specific color cartridge that is reporting as empty (e.g., Cyan or Magenta).
5. When the prompt asks if you have replaced the ink, select Yes. This tricks the internal counter into believing a new cartridge has been installed, resetting the ink level to 100% in the software.
6. Press the Home button again to resume normal operations.
7. Perform a "Print Quality Check Sheet" from the Ink menu to ensure no air bubbles have entered the lines.

If That Didn't Work

• Hard Reset the Ink Logic: Power down the machine and unplug the power cord for exactly 60 seconds. While unplugged, hold the power button for 10 seconds to discharge the capacitors. Plug it back in and restart. This often forces the printer to re-poll the cartridge chips.
• Reseat the Cartridges: Open the ink cartridge cover and physically remove the tank that is reporting empty. Inspect the gold contact chips on the cartridge for ink smears or dust. Clean the chips gently with a lint-free cloth dampened with 90% isopropyl alcohol. Reinsert the cartridge firmly until it clicks.
• Run a Deep Cleaning Cycle: Go to Settings > Maintenance > Cleaning All. Select "Strong" or "Deep" cleaning. This forces the pump to pull ink through the lines, which can sometimes clear a "clogged" sensor reading that the printer interprets as an empty tank.
• Update Firmware: Access the Brother firmware update utility on your PC. If the MFC-J4535DW is running an outdated version, the ink estimation algorithms may be flawed. Updating to the latest version often corrects these false-empty triggers.

Heads Up

• Avoid Total Depletion: While bypassing the alert is useful, never let the tanks actually run dry. If air enters the print head, you will experience permanent banding that requires a professional service technician to fix.
• Use Genuine LC450X/LC451: Using third-party "refillable" tanks often causes the chip to mismatch, leading to constant 'Replace Ink' errors even when full.
• Monitor the Window: Trust the physical ink window over the screen. If the ink level drops below the 20% mark visually, replace the cartridge immediately regardless of what the software says.
• Cleaning Cost: Remember that "Deep Cleaning" cycles consume a significant amount of ink. Overusing this feature to clear errors will actually empty your tanks faster than printing documents.